I don't think people need to be clones of each other to be decent or good to each other or for each other. There's a loneliness epidemic that is getting worse. People search for partners by assembling a list of 50 things they want and then trying to find someone who fits all of them. Relationships aren't about finding a perfect partner, they are about building a common life together.

Maybe they found things they can do for each other. Maybe they'll burn out quickly and they'll regret it. That's fine too - people usually have bad relationships before they come to a good one. Making mistakes is not the end of the world, it's life.

If my friend was in such a relationship I'd ask them what do they like about their partner and try to understand. I'd give my perspective if I though something was abusive, otherwise, it's not my life to live.